The BP oil spill in the Gulf of Mexico resulted in large areas of crude oil floating on the ocean surface. Some of these areas are close to beaches or natural habitats of animals. Mechanical recovery, chemical treatment, bioremediation, and in-situ burning are amongst the most widely practiced marine oil spill response technologies.
While large scale skimming is one method to control oil pollution, the U.S. Coast Guard has been conducting in-situ burns of the surface oil, primarily due to the advantages associated with this technology such as high oil removal rates, relatively low cost, and simple logistics.
The U.S. Coast Guard issued an operations manual for in-situ burning of oil from oil spills as U.S. Coast Guard Research and Development Center Report No. CG-D-06-03, Oil Spill Response Offshore, In-Situ Burn Operations Manual, Final Report, March 2003 (hereinafter, Coast Guard Manual). The Coast Guard Manual may be referred to for conventional in-situ burning of oil pools floating on water.
The problem of burning oil in the ocean surface is that favorable combustion conditions are rarely achievable, particularly towards the center of the fire where oxygen availability is limited due to lack of air entrainment. As a result, a black smoke plume from the in-situ burn can rise hundreds or even thousands of meters. The Coast Guard Manual described adding chemical smoke inhibitors such as ferrocene. But its use is not approved due to high cost, difficulty of applying, and potential toxicity. While the black smoke may have less environmental impact than the oil slick, the public generally finds the black smoke plume objectionable.
A further problem of the in-situ burn is that a substantial amount of oil is still left unburned after the fire self-extinguishes, that is, after a minimum flame-sustainable oil layer thickness is reached as reported in the Coast Guard Manual.
A method to burn the oil cleanly with substantially less smoke and/or to reduce the residual oil after fire extinction is desired.
Another problem with oil floating on water is the formation of a stable water-in-oil emulsion which will reduce the window of opportunity for in-situ burning. The presence of a critical amount of water in the oil prevents the slick in contact with the ignition source from catching fire as reported in the Coast Guard Manual.
A method to increase the window of opportunity for in-situ burning by providing conditions for burning emulsified oils is desired.